The invention relates to methods for the manufacture of compacts from comminuted material such as lignocellulose material and/or other combustible material, an apparatus for practicing the methods, and to a multi-platen press for the apparatus.
DE 199 55 844 A1, from which the invention sets out and which is incorporated here by reference, relates to a method and a press for the manufacture of pellets. Accordingly, pellets for heating purposes consist of compressed biomass, such as sawdust and/or planer chips, the starting material being able to contain also wheat and corn in ground form or starch in the amount of 1 to 10 weight-percent which is added to the mixture as lubricant and binder. The corresponding press is a ring or flat die press with, pug rolls which in the circuit force the material through the openings in a hole plate and thus produce pellets or compacts.
Such wood pellets have diameters of 4 to 10 mm and are shorter than 50 mm. Wood briquettes have different shapes, the diameter being 20 mm. Both are compacts with a density greater than 1000 kg/m3, preferably greater than 1200 kg/m3. They are used for heating in hearths, special combustion stoves and other hearths and are appropriate due to their free-flowing quality for automatic firing. The material, for the manufacture of the compacts can also be made of materials other than those containing lignocellulose, as for example annual plants (e.g., straw, bagasse, . . . ), palms, peat or certain types of brown coal, or mixtures of various materials containing lignocellulose. For the disposal of plastics (e.g., thermosetting plastics), 5% to 50% of such waste can, be admixed with the lignocellulose material. On the other hand the exhaust gases produced by burning must of course be especially filtered. In the case of pellet and briquette production, the starting material is generally comminuted materials in the form of chips.
Pursuant to DE 26 00 648 C2 and U.S. Pat. No. 3,743,462, which are incorporated here by reference, the ground material are forced by means of rolls through a hole plate. In the case of wood briquetting, extrusion presses are used as a rule. Pellet presses and extruders have the disadvantage that the capacity per machine is limited to a maximum of 3 metric tons per hour. In the case of pelletizing, an adhesive such as starch, for example, must be added in an amount of up to 2% of the dry wood mass, since the compaction achieved of up to 1300 kg/m3 is not enough to achieve sufficient strength without binding agent. Furthermore, the electric power consumption is relatively great and uneconomical. Theoretically, ordinary chipboards can be made, cut up in continuous twin-belt presses or single or multiple stage presses and used as fuel. But when the chip boards are cutup with saws, sawdust is produced and the minimum saw kerf amounts to about 3 mm. The compact is thus not round and therefore it is relatively unsuitable for automatic stoking. Also, in the case of chips 10 mm thick, 15% sawdust is produced. Any accurate cutting of the high-density compact is likewise difficult.